The Jewish calendar, like the Chinese calendar, is a lunisolar calendar. This means that the Jewish calendar is a combination of a solar calendar and a lunar calendar. The Jewish calendar attempts to have the year coincide with the solar calendar and its months coincide with the lunar calendar. Since the twelve months of the Jewish calendar are about eleven days short of a 365-day year, a leap month is added to the calendar on a 19-year cycle developed by Hillel II in the fourth century. The current cycle began in 5758 (1997-1998). An extra month is added on the third, sixth, eighth, eleventh, fourteenth, seventeenth, and nineteenth years during this cycle. (This is why one will see Adar I and Adar II on some calendars).

The year is calculated as the number of years since creation (5772 = September 2011 - September 2012). The year was calculated by adding up the ages of people in the Tanach back to the time of creation. However, this does not necessarily mean that the universe has existed for only 5770 years as we understand years. An ordinary Jewish calendar year has 353-355 days and a leap year has 383-385 days. Each month begins on Rosh Chodesh  (new moon).

Before the Babylonian Exile, the months of the Jewish calendar were remembered by numbers and not names. The first month of the Jewish calendar is Nisan - however, it was referred to as "the first month". According to Maimonides (Talmud Yerushalmi-Rosh Hashannah 1:2), the names for the months came with the Jews when they returned to Israel from their Babylonian exile. 

Months of the Year

* Leap year only
** Adar II in Leap Years

Days of the Week